Both `Cr_(2)O_(7)^(2-)` (aq) and `MnO_(4)^(-)` (aq) can be used ot titrate `Fe^(2+)`(aq) if in a given titration 24-50 `cm^(3)` 0.1 M `Cr_(2)O_(7)^(2-)` were used then what volume of 0.1 M `MnO_(4)^(-)` solution would have been use for the same titration ?

Answer

29.4 `cm^(3)`

Explanation

The balaced redox reaction involving oxidation f `Fe^(2+)` ions by `Cr_(2)O_(7)^(2-) "and" MnO_(4)^(-)` respectively are
`Cr_(2)O_(7)^(2-)+6Fe^(2+)14H^(+)rarr2Cr^(3+)+6Fe^(3)+7H_(2)O`
`MnO_(4)^(-)+5Fe^(2+)+8H^(+)rarrMn^(23+)+5Fe^(3+)+4H_(2)O`
Suppose `V_(2) cm^(3) "of" M_(2)F^(2+)` is titreated against 24.50 `cm^(3)` of 0.1 M `Cr_(2)O_(7)^(2-) "and" V_(1)cm^(3) of 0.1 M MnO_(4)^(-)`
solution then
`(24.5xx0.1)/(1)(Cr_(2)O_(7)^(2-))=(M_(2)B_(2))/(6)(Fe^(2+))`
`(V_(1)xx0.1)/(1)(MnO_(4)^(-))=(M_(2)V_(2))/(5)(Fe^(2+))`
Equating (i) and (ii) `V_(1)=2.45xx6/5=29.4 cm^(3)`